|Comets: Windows Into Time - NASA|
Presents three parts on comets. Reveals that comets were born with the sun some 4.5 billion years ago but, unlike planets, the primitive ice and dust of coments have remained unchanged. Shows that they are windows into time, into the origins of the solar system. Defines comets and gives a historical account of them, including Halley’s comet in Part One. Looks at new studies investigating comets at short range, presently only from observations on Earth, but new space probes will allow the close...
Keywords: NASA, comets, Halley's comet, astronomy